The disclosure relates generally to methods of improving the performance of particulate filters and particularly to methods of enhancing the ash storage capacity of particulate filters.
Particulate filters are an essential component of modern diesel after-treatment systems and may see increased application in gasoline after-treatment systems. Commonly used wall-flow filters operate with a combination of depth filtration and surface filtration, the former being primarily performed by the filter wall material and the latter by a layer of soot and ash particulates deposited onto the filter wall during operation. The ash particles originate from inorganic components in the fuel and lubricant oil. In contrast to soot particles, ash particles do not burn during filter regeneration and accumulate over time, forming an ash wall layer as well as channel plug ash. This leads to a gradually increasing pressure drop across the filter and a penalty in fuel efficiency. At a certain point, the filter pressure drop exceeds an acceptable range.
A variety of methods have been proposed to remove ash from filters. Many of such methods require periodic maintenance in a service station using specifically designed ash cleaning apparatuses. Such methods include mechanical vibration, reversed air pulsing, gravity force, or acoustic wave. Methods of removing ash from filters in-situ (i.e., while the filter is on engine) are less common. One proposed method involves thermally sintering the ash at temperatures ranging from 700-1000° C. However, this method suffers from drawbacks, which include the sintered ash being more difficult to remove, the high temperature required introduces a fuel penalty, and the exposure of the filter and any catalyst(s) to high temperatures, raising concerns relating to ash interaction with filter materials, filter thermal-mechanical robustness, and catalyst deactivation.